Heavy metals removal from soil/sediments washing effluents via biocompatible aqueous two-phase systems

Abstract

The generation of high amounts of soil/sediment washing solutions is one of the main concerns faced in ex situ treatment techniques, so in the present research, we have demonstrated the suitability of an organic salt like sodium potassium tartrate to efficiently promote phase segregation in a model soil washing solution containing biodegradable non-ionic-surfactants (Tween 80 and Tergitol 15S9) and heavy metals (copper, zinc, and cadmium), after a preliminary screening of the demixing effect of different inorganic and organic salts like ammonium nitrate, ammonium acetate and sodium potassium tartrate. The aqueous two-phase systems were characterized in depth at room temperature by defining the immiscibility region and correlating the experimental data with three empirical equations, and the results were discussed in the light of a thermodynamic function like the Gibbs free energy of hydration. Then, the applicability to extract the abovementioned metal ions was researched after TLs determination, observing high heavy metals extraction percentage (over 80 % in some cases). The extraction process was included in the soil washing process at real scale and it was simulated by means of the software SuperPro Designer, that makes up a valuable tool to ease the analysis of the technical viability of the proposed strategy.